Trimmable trusses have been used with increasing frequency in certain applications, for example, in light commercial and warehouse buildings, where there is no standard length (ie. stock length) of commercially available trusses. Instead, one or both ends of a longer trimmable truss may be cut-off, ie. trimmed, so that the trimmed truss is of the desired length for a given application. Such trimmable trusses can be inventoried in standard lengths. Such trimmable trusses must be capable of withstanding substantial live, dead, and seismic loading as well as twisting, particularly when used in earthquake-prone areas.
Known prior art trimmable trusses have proved unsatisfactory, particularly in the longer lengths with heavy loads, ie. of approximately 24 feet or more. For example, one known trimmable truss is believed suitable for certain light duty load applications, such as in residential uses of approximately 20 feet or less in length. When they are used for application lengths longer than that, the design of that type known truss is such as to cause it to often twist, deflect, and fail. This is particularly the case when one (or both) trimmable ends of the truss is substantially trimmed away.
Other trimmable trusses are known but also have deficiencies. For example, with one truss the nailing or so-called gusset plates are located within the trimmable area, requiring either their total removal or otherwise preventing the truss from being easily trimmed to a desired specific length (ie. if trimmed where the gusset plates are located).
The present invention overcomes these deficiencies in the prior art by providing a trimmable truss having elongated upper and lower chords which have ends extending beyond the respective final verticals to create a trimmable area at each end. Separate insertable trim members are interconnected between the respective sets of upper and lower chord extension members. The gusset plates used for the last verticals as well as the last diagonal webs are designed to fasten the insertable trim member into the trimmable end section. This is done to preserve, ie. to protect, the integrity of the truss at the respective trimmable ends, and thus, to prevent failure. Further, the respective last diagonal web members are aligned in an upwardly rising position so as to be in tension. This, in turn, allows any remaining (ie. untrimmed) trimmable end section to be in compression, all so that it may accept substantial force loadings placed thereon. In the preferred embodiment, the separate insertable trim members comprise a portion of a so-called wooden, solid web I-beam, a commercially available component having separate upper and lower sub-chord members interconnected by a vertical plywood or particle board (ie. so-called OSB) web member. In an alternative embodiment, the separate insertable trim members comprise a portion of glued laminated beam.
The present improved method of making a trimmable truss includes forming a truss unit having elongated upper and lower chord members interconnected by a series of alternate opposite-aligned diagonal webs (with or without vertical webs); forming the last diagonal web at each end to be in an upwardly rising alignment; inserting final verticals at the respective ends of the series of diagonals; extending the respective upper and lower chords beyond the final verticals; inserting a trim member between the extended chords, each insertable trim member being a portion of either a wooden I-beam or a glued laminated beam; and overlapping gusset plates substantially into the respective trimmable end sections so as to protect the integrity of the truss member adjacent the final vertical.
The present type trimmable truss is aimed at both the residential and commercial/industrial market. The typical truss length required is from 16 feet to 40 feet. In commercial applications, such as used for warehouses or offices, the trusses are typically placed on 16 inches to eight foot centers. They are attached to the supporting structure by hangers using nails or bolts. The typical vertical dimension for the present improved trimmable wooden truss is between 16 and 30 inches high. In residential applications, the present trusses are typically placed on 16 inches to two foot centers.
Thus, it is an object of the present invention to provide an improved trimmable truss which permits either or both its respective ends to be trimmed within limits, and provide structural integrity regardless of the end amount that is trimmed.
It is a further object of the present invention to provide an improved trimmable truss which utilizes separate insertable trim members, having sub-chord members, so as to provide substantial additional structural integrity to the respective trimmable end sections and to the overall truss when trimmed.